Many people having an injury or illness suffer from decreased mobility or range of motion in for instance an arm or a leg. Such reduction in mobility can result in atrophy of remaining viable good muscle tissue. Often, such persons, if they had a means of exercising their remaining good muscles, could increase their strength and mobility but for a means to engage in such exercise. For instance, if a person could move their arm in a planar (flat) motion when subject to little or reduced resistance, such person could benefit from such exercise. However, because most surfaces where the person would otherwise move their arm are not adapted to providing for reduced resistance, such person is not readily able to avail himself to such beneficial exercise. Various devices such as traction devices or crutches or the like are known and are used in rehabilitation in for persons having an injury or illness that has caused reduction of mobility in such persons. However, such devices are often highly specialized to a particular rehabilitation task and/or are relatively complex and/or expensive, and are not adapted to providing for the reduced resistance motion.